1. Field of the Invention
The present invention is directed to a method and apparatus for catheter navigation in three-dimensional vascular tree exposures, in particular for intracranial application, of the type wherein the position of the catheter is detected and mixed into the 3D image of the preoperatively exposed vascular tree reconstructed in a navigation computer, and wherein imaging (registering) of 3D patient coordinate information ensues with a 3D image coordination system prior to the intervention using a number of markers placed on the patient's body, the position of these markers being registered by the catheter.
2. Description of the Prior Art
The treatment of vascular pathologies, in particular intracranial vascular pathologies, frequently ensues with the aid of a catheter that is inserted into the femoral artery and is guided through the blood vessels to the location of the treatment site. This procedure is implemented using continuously pulsed 2D-radioscopy (frequently with biplanar systems) and a contrast medium. It is often difficult for the neuro-radiologist to bring the 2D radioscopic images into coincidence with the complex three-dimensional shape of the real vascular tree. Another disadvantage of this known method is that the necessity of continuously implementing the radioscopy during the intervention entails radiation exposure for the physician and patient, and requires that the injected contrast medium be present during the entire catheter treatment, so that contrast agent must be constantly re-injected, which can have a toxic effect.
Three-dimensional images of the vascular tree can be produced by different imaging modalities, such as e.g. magnetic resonance angiography (MRA), computed tomography angiography (CTA) and 3D angiography. In 3D angiography, a 3D volume of the vascular tree is reconstructed and visualized from several, approximately 50, preoperative or intraoperative 2D x-ray projection images taken from different angles, these images generally being acquired using a C-arm x-ray device. The neuro-radiologist obtains a 3D image of the vascular tree by means of 3D exposure techniques, but has no direct knowledge about the current position of the catheter in this 3D vascular tree during the intervention. The physician must mentally image the intraoperative 2D radioscopy images, in which the catheter is depicted, onto the preoperatively scanned and reconstructed 3D vascular tree in which the catheter is not depicted, which can be laborious and time-consuming given complex vascular tree structures.
Detecting the position of the catheter using a position detection system and mixing a representation thereof into the reconstructed, three-dimensional vascular tree exposures is known, although the imaging of the 3D patient coordinate system data onto the 3D image coordinate system poses significant difficulties.
A method is disclosed in U.S. Pat. No. 5,851,183, in which the tip of a probe is detected by a position detection system and is represented in an image together with an x-ray exposure taken at the same time. In this procedure, however, only that slice is depicted from the acquired tomograms (of course, using the tip of the probe) in which the probe tip is currently located. This is, however, not comparable to the mixing a representation of a catheter tip into a three-dimensional image, to allow the catheter to be guided on the basis of this mixing so that a physician can reach the desired locations of branches of blood vessels or such. In addition, in the method according to U.S. Pat. No. 5,851,183, it is necessary to produce x-ray images with virtually no interruptions during the examination, which represents a very significant radiation exposure for the patient that one would optimally like to avoid.